11 Endophytes as Plant Nutrient Uptake-Promoter in Plants
257
Cu, Zn, etc., by controlling soil pH (Wenzel 2009). In this context, eukaryotes are
more sensitive to metal toxicity in comparison to that of prokaryotes, i.e. bacteria,
and their typical mechanisms to regulate metal concentration is the expression of
some metal-chelating proteins such as metallothioneins (Durán et al. 2011). The
easiest mechanisms for the endophytes to regulate metal uptake by plants could be
explained by the extracellular immobilization and/or cell wall binding. Thus, Green
and Clausen (2003) observed the use of chelators in immobilizing metals in the soil.
Such chelators are mainly organic acids as citrate and oxalate, easily created by fungi
(Marina et al. 2019; Odoni et al. 2017).
Bilal et al. (2018) co-inoculated Sphingomonas and Paecilomyces formosus and
bacteria Sphingomonas sp. in soybean plants; an improvement was observed in plant
growth under Al and Zn stresses. The inhibition in the metal uptake and translocation
resulted in the enhancement of the nutrients uptake caused by the endophyte and
modulate soil extracellular enzymatic activities. Ikram et al. (2018) found the IAA
producer endophyte Penicillium roqueforti to increase the uptake of several nutrients,
showing a low concentration of heavy metals in shoot and roots when allowed to grow
in wastewater. This increase in nutrients uptake by plants growing in contaminated
soils was mainly due to their association with endophytes (Khan et al. 2010), which
increased the solubility of the nutrients of the soil. DSE fungus Exophiala pisciphila,
can accumulate Pb and Cd up to 20% and 5% dry weight, respectively, in the roots
(Zhang et al. 2008). This fact is especially interesting in pasture species growing in
metal-polluted soils because the accumulation might take place in roots, remaining
the aerial part of these plants thus, acted as safe feed to the animals. Thus, the
poisoning by lead of the cattle, which is the most reported cause of poisoning in farm
livestock (Suttle 2010), might be, at some extent, avoided. Inoculation with Mucor
sp. in some plants of Brassicaceae in degraded soils due to heavy metals (van der
Ent et al. 2013; Verbruggen et al. 2009) resulted in lower metal accumulation in
plant tissues. Facilitating metal transport from the cytosol into the vacuole help in
increasing metal tolerance of its plants (Rozpadek et al. 2018).
Always depending on the interaction of the symbiont with the environmental
conditions (Ahlholm et al. 2002), a large number of fungal endophytes induce growth
and development in polluted soils that occurred due to the removal of heavy metals
as summarized in Table 11.3. Various workers (Dennis et al. 1998; Soleimani et al.
2010; Soto Barajas et al. 2016) reported that endophytes can be considered as a
solution for cropping in heavy metal-polluted areas. Likar and Regvar (2013) showed
that Phialophora endophytes allowed Salix plants to live and grow normally in Cdpolluted soils due to the decrease in the metal uptake. Reductions in the Cu uptake by
plants were also reported by Zabalgogeazcoa et al. (2006), while Monnet et al. (2001)
and Malinowski and Belesky (1999) indicated a decrease of Cu and Al uptake by
plants. Lledó et al. (2015, 2016, 2017) reported the endophytic fungus Stemphylium
globuliferum to cause a dicrease in the Al content in the aerial biomass of legumes
and in the Cr concentration in herbage of P. pratensis when cultivated in greenhouse
conditions. However, field experiments with the same endophyte in subterranean
clover showed an increase in the Al content in aerial biomass of the plant (Lledó
et al. 2016). More consistent results were obtained in case of endophyte Fusarium
257
Cu, Zn, etc., by controlling soil pH (Wenzel 2009). In this context, eukaryotes are
more sensitive to metal toxicity in comparison to that of prokaryotes, i.e. bacteria,
and their typical mechanisms to regulate metal concentration is the expression of
some metal-chelating proteins such as metallothioneins (Durán et al. 2011). The
easiest mechanisms for the endophytes to regulate metal uptake by plants could be
explained by the extracellular immobilization and/or cell wall binding. Thus, Green
and Clausen (2003) observed the use of chelators in immobilizing metals in the soil.
Such chelators are mainly organic acids as citrate and oxalate, easily created by fungi
(Marina et al. 2019; Odoni et al. 2017).
Bilal et al. (2018) co-inoculated Sphingomonas and Paecilomyces formosus and
bacteria Sphingomonas sp. in soybean plants; an improvement was observed in plant
growth under Al and Zn stresses. The inhibition in the metal uptake and translocation
resulted in the enhancement of the nutrients uptake caused by the endophyte and
modulate soil extracellular enzymatic activities. Ikram et al. (2018) found the IAA
producer endophyte Penicillium roqueforti to increase the uptake of several nutrients,
showing a low concentration of heavy metals in shoot and roots when allowed to grow
in wastewater. This increase in nutrients uptake by plants growing in contaminated
soils was mainly due to their association with endophytes (Khan et al. 2010), which
increased the solubility of the nutrients of the soil. DSE fungus Exophiala pisciphila,
can accumulate Pb and Cd up to 20% and 5% dry weight, respectively, in the roots
(Zhang et al. 2008). This fact is especially interesting in pasture species growing in
metal-polluted soils because the accumulation might take place in roots, remaining
the aerial part of these plants thus, acted as safe feed to the animals. Thus, the
poisoning by lead of the cattle, which is the most reported cause of poisoning in farm
livestock (Suttle 2010), might be, at some extent, avoided. Inoculation with Mucor
sp. in some plants of Brassicaceae in degraded soils due to heavy metals (van der
Ent et al. 2013; Verbruggen et al. 2009) resulted in lower metal accumulation in
plant tissues. Facilitating metal transport from the cytosol into the vacuole help in
increasing metal tolerance of its plants (Rozpadek et al. 2018).
Always depending on the interaction of the symbiont with the environmental
conditions (Ahlholm et al. 2002), a large number of fungal endophytes induce growth
and development in polluted soils that occurred due to the removal of heavy metals
as summarized in Table 11.3. Various workers (Dennis et al. 1998; Soleimani et al.
2010; Soto Barajas et al. 2016) reported that endophytes can be considered as a
solution for cropping in heavy metal-polluted areas. Likar and Regvar (2013) showed
that Phialophora endophytes allowed Salix plants to live and grow normally in Cdpolluted soils due to the decrease in the metal uptake. Reductions in the Cu uptake by
plants were also reported by Zabalgogeazcoa et al. (2006), while Monnet et al. (2001)
and Malinowski and Belesky (1999) indicated a decrease of Cu and Al uptake by
plants. Lledó et al. (2015, 2016, 2017) reported the endophytic fungus Stemphylium
globuliferum to cause a dicrease in the Al content in the aerial biomass of legumes
and in the Cr concentration in herbage of P. pratensis when cultivated in greenhouse
conditions. However, field experiments with the same endophyte in subterranean
clover showed an increase in the Al content in aerial biomass of the plant (Lledó
et al. 2016). More consistent results were obtained in case of endophyte Fusarium